No Problem

In answer to 'no problem'.

So you call customer service and tell them that the delivery didn't arrive, or you take your sandwich back to the counter because the wrapper says it's tuna but the contents are ham - and the reply is 'No problem', and they deal with the error.

Except it is their error and they have no locus, no standing to be saying it is no problem.

It is a problem and they caused it.

So after the zillionth time this happens, you mention it. You explain that the phrase is inappropriate to the situation.

And their eyes cross with confusion because they don't understand.

When you probe a bit deeper they tell you it is just an expression that has no meaning other than as an acknowledgement.

You ask them how they would feel if the situation were reversed.

How would they feel if they got the wrong sandwich and had to stand up and leave their coffee on the table, (hoping a waiter wouldn't scoop it up, thinking they'd left) and then break into the queue and suffer the looks from the other waiting customers.